Small motor with improved connecting structure between coil, riser and varistor

ABSTRACT

When winding an armature coil, start S of a winding is entwined around a riser R 1,  the wire is wound via a riser R 4  around a salient pole P 1  adjacent to the riser R 4  and an opposed salient pole P 2  to the salient pole P 1  in order, and leads from a riser R 3  through an opposed riser R 6  to an adjacent salient pole P 3  and an opposed salient pole P 4.  Next, the wire is passed to a riser R 5  and is wound around an opposed riser R 2,  an adjacent salient pole P 5,  and a salient pole P 6,  then ends with the riser R 4.  A varistor  18  is inserted and three electrodes  19  are soldered to the corresponding risers R 2,  R 4,  and R 6.

This is a continuation of application Ser. No. 09/627,325 (now U.S. Pat.No. 6,285,109 issued Sep. 4, 2001) filed Jul. 27, 2000, which is acontinuation of application Ser. No. 09/132,774 filed Aug. 12, 1998 (nowU.S. Pat. No. 6,153,960 issued Nov. 28, 2000), the disclosures of eachof which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

2. Related Art

As shown in FIG. 5, generally, in a structure of an armature 50 of asmall brush DC motor of a 4-6 (4-magnetic-pole—6-salient-pole)structure, for wiring of coils 53 wound around six radially projectingsalient poles 52 of an armature core 51 and six risers 55 electricallyconducting as terminals of six commutators 54, a circuit is previouslyformed with a substrate or electrode print pattern 57 (hatched portionin the figure) formed as a thick film on one side of a ring varistor 56,the windings of the coils 53 wound around the six salient poles 52 areconnected to the six risers 55 extended from the corresponding sixcommutators 54, and the electrode print pattern 57 of the ring varistor56 are joined to the faces of the risers 55 by soldering 58, forming thearmature 50.

The electrode print pattern 57 illustrated in FIG. 5 is a circuitpattern conducting so that a pair of two long and short risers formedinterposing the rotation center of the armature therebetween becomes thesame potential; three circuit patterns for the three pairs of risers areformed in the same shape and electrically independent of each other.

That is, the circuit pattern for electrically connecting a pair ofrisers, for example, extends from one long riser round the outside of ashort riser in another pair adjacent to the pair through the lower sideof a long riser in still another pair adjacent the pair to theassociated short riser. The three circuit print patterns 57 are formedon one side of the ring varistor 56 and a pair of long and short risersis connected by soldering 58 for each print pattern 57. Further, thethree circuit patterns are placed so as to separately contain threeelectrodes disposed in the ring varistor 56 and are electricallyconnected.

The above-described wiring structure uses the circuit formed in the ringvaristor 56 as a part of a current diverting circuit of the coil 53 bythe commutator 54.

However, to flatten and miniaturize a motor, it is difficult to placethe electrode print pattern 57 in the ring varistor 56 and the ringvaristor 56 is specifically designed and manufactured; it is unavoidablethat the product becomes expensive.

Further, if the electrode print pattern 57 placed in the ring varistor56 becomes small, it easily comes in contact with another pattern andpositioning accuracy with the risers 55 becomes strict; it is fearedthat an electric short circuit may be produced when coil terminals areconnected or soldered.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to apply a normal ringvaristor provided with three electrodes used with a general armature ofa 2-3 (2-magnetic-pole—3-salient-pole) structure having three electrodeparts in an armature in a 4-6 structure. It is accomplished by a coilwinding method around salient poles that a normal 3-electrode varistorprovides an overvoltage suppression effect equal to that of a varistorspecifically designed for an armature of a 4-6 structure.

It is more particularly to solder three of six risers directly to threeelectrodes of a varistor together with coil winding terminals and solderonly coil winding terminals to the remaining three risers each betweenthe electrodes of the varistor for forming an armature, in short, routea coil winding around salient poles in a manner of drawing with a singlestroke of a brush containing connection to the risers.

According to an aspect of the present invention, there is provided asmall motor comprising:

an armature having six salient poles radially and a coil wound aroundthe salient poles;

six risers connected to said coil;

commutators being joined to said risers in a one-to-one correspondence;

a ring varistor being connected to said riser for suppressingovervoltage;

a brush coming in sliding contact with said commutator for supplying acurrent; and

a permanent magnet having four magnetic poles, placed facing the salientpoles,

wherein said coil includes one wire wound continuously around the sixsalient poles and the six risers from a winding start terminal to awinding end terminal and said ring varistor is provided with threeelectrode parts to which alternate three of said six risers areconnected.

As described above, according to the small motor according to theinvention, a general ring varistor used with an armature of a 2-3(2-magnetic-pole—3-salient-pole) structure can be applied to a devicefor extinguishing spark arcs for suppressing overvoltage of an armatureof a 4-6 (4-magnetic-pole—6-salient-pole) structure without specialworking and moreover a special wiring pattern is not used, thuspart-to-part accuracy is not required and the structure and partsmanagement can be simplified sufficiently.

Because of coil winding according to a pattern drawn with a singlestroke of a brush, automation is facilitated and productivity can beimproved. Further, the varistor can be miniaturized, so that thearmature itself can be well fitted to miniaturization.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a plan view of one embodiment of an armature of a small motoraccording to the invention and FIG. 1b is a sectional view taken on lineB—B in FIG. 1a ;

FIG. 2a is a schematic diagram and FIG. 2b is a wiring diagram todescribe a winding pattern of armature coil windings of the small motoraccording to the invention;

FIG. 3a is an expansion diagram of FIG. 2a to a pattern drawn with asingle stroke of a brush to describe the armature coil windings of thesmall motor according to the invention and FIG. 3b and 3 c are otherexpansion diagram examples of patterns drawn with a single stroke of abrush;

FIG. 4 shows embodiments of varistors used with the small motoraccording to the invention; 4 a is a plan view of a varistor formed withelectrode parts on an outer peripheral side face and 4 b is a plan viewof a varistor formed with electrode parts on one face; and

FIG. 5 is a plan view of an armature of a small motor in a related art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of a small motor according to the invention will bediscussed with reference to the accompanying drawings. FIG. 1a is a planview to show an armature 10 of a small brush DC motor and FIG. 1b is asectional view taken on line B—B in FIG 1 a. The structure of the smallmotor containing a brush coming in sliding contact with a commutator 15for supplying a current and a permanent magnet having four magneticpoles, placed facing salient poles is known and is not shown.

A shaft 12 is inserted into the center of an armature core 11 and fixedand an insulator or insulating coating for electrically insulating coils14 wound around salient poles P1-P6 is applied to the surface of thearmature core 11, then a commutator holder 20 for separately insulatingsix commutators 15 joined to risers R1-R6 integrally and supporting inintegral mold of insert (or outsert) mold is fixed to a predeterminedposition of the shaft 12 on one side of the armature core 11. A coilwinder (not shown) is used to wind coils 14 around the salient polesP1-P6 extending radially from the center of the armature core 11 andeach having a bow-shaped part 16 in the outer peripheral portion.

The winding means is schematically shown in FIG. 2a and a wiring diagramthereof is as shown in FIG. 2b. The illustration in FIG. 2a isfurthermore expanded as a plane to a pattern drawn with a single strokeof a brush shown in FIG. 3a. For clarification, in FIG. 3a -3 c, theportion of the first pair of risers and a salient pole coil winding fromthe winding start and the portion of a pair of risers and a salient polecoil winding at the winding end are indicated by solid lines and theportion of an intermediate pair of risers and an intermediate salientpole coil winding is indicated by the dashed line. Although the lines inFIG. 3 are cut at both ends, A, B, C, and D shown corresponding to theleft and right terminals of the lines are concatenated with thecorresponding parts (letters) and the winding start S to the winding endE is formed by one continuous line as will be appreciated by thoseskilled in the art, of course.

Reference numerals P1-P6 indicating the salient poles and R1-R6indicating the risers in FIG. 3a to 3 c correspond to placement of thesalient poles and the risers shown in FIG. 2a. Winding of coil 14 andwinding 17 in a similar manner to the pattern drawn with a single strokeof a brush will be discussed with reference to FIG. 2a and FIG. 3a.

In FIG. 2a and FIG. 3a, when winding start S of the winding 17 (solidline) is entwined around the riser R1, the wire is wound via the opposedriser R4 symmetric with the riser R1 with respect to a point of therotation center of the armature core 11. Next, the wire is wound aroundthe salient pole P1 adjacent to the riser R4 and the opposed salientpole P2 symmetric with the salient pole P1 with respect to a point ofthe rotation center of the armature core 11 in order. The coil with afirst phase (for example U phase) of three phases is continuously woundon the passing way defined by R1-R4-P1-P2 without interruption. Theriser R1 is not connected to the electrode part 19 of the varistor 18and the riser R4 is connected to the electrode part 19 of the varistor18 to suppress an over-voltage caused in the first phase. Next, thewinding 17 exits the left line terminal A, enters the right lineterminal A, is entwined around the riser R3, through the opposed riserR6, (dotted line) exits the left line terminal B from the adjacentsalient pole P3, enters the right line terminal B, and leads to theopposed salient pole P4. The coil with a second phase (for example, Vphase) of the three phases is continuously wound on the passing waydefined by R3-R6-P3-P4 without interruption. The riser R3 is notconnected to the electrode part 19 of the varistor 18 and the riser R6is connected to the electrode part 19 of the varistor 18 to suppress anover-voltage caused in the second phase. Next, the winding 17 is passedto the riser R5, (solid line) is entwined around the opposed riser R2,exits the right line terminal C from the adjacent salient pole P5,enters the left line terminal C, is wound around the salient pole P6,and the winding end terminal E is entwined around the riser R4. The coilwith a third phase (for example, W phase) of the three phases iscontinuously wound on the passing way defined by R5-R2-P5-P6 withoutinterruption. The riser R5 is not connected to the electrode part 19 ofthe varistor 18 and the riser R2 is connected to the electrode part 19of the varistor 18 to suppress an over-voltage caused in the thirdphase.

This is represented as a string of the reference numerals (letters) asfollows: S-R1-R4-P1-P2-(left A-right A)-R3-R6-P3-(left B-rightB)-P4-R5-R2-P5-(right C-left C)-P6-R4-E. FIG. 3b and 3 c show otherexamples of patterns drawn with a single stroke of a brush. Forsimplicity, they are described in a similar manner that shown above.

FIG. 3b : S-R1-R4-P1-(right A-left A)-P2-R6-R3-(right B-leftB)-P3-P4-R2-(left C-right C)-R5-P5-(right D-left D)-P6-R4-E.

FIG. 3c : S-R1-R4-P1-P2-(left A-right A)-R3-R6-P3-(left B-rightB)-P4-R5-R2-P5-(right C-left C)-P6-R4-E.

According to any of such patterns, the coil 14 is wound around thesalient poles P1-P6 containing connection to the risers R1-R6. That is,for the winding 17, a wire is wound around the salient poles P1-P6, thenis entwined around the terminals of the risers R1-R6 from one salientpole to another. FIG. 3b is electrically equivalent to FIG. 3aindependently of the connection order because the connection order ischanged only in the two pairs of risers (R3 and R6 and R5 and R2) inFIG. 3a and the paired risers are the same potential. FIG. 3c differsfrom FIG. 3a only in how to route the winding 17; they are the same inthe winding order around the salient poles and the risers. The patternsshown in FIG. 3a -3 c are examples and any other pattern is alsosufficiently possible if it is a pattern drawn with a single stroke of abrush, needless to say. Although it is best that a single wire is woundfrom the first phase to the third phase in the workability, if the coilis independently wound on each phase, it is appropriate to apply thering varistor with three electrode parts to the 4-6 structure motor whenthe wiring pattern is improved as shown in FIGS. 3(a) to (c).

Next, as shown in FIG. 1b, a varistor 18 is fitted into the outerdiameter of a commutator holding ring 21 from the opposite side (topface in the figure) to the armature core 11 with respect to thecommutator holder 20. The outer diameter of the commutator holding ring21 is formed so as to show a loose fit to an annular inner face 22 ofthe varistor 18 for suppressing damage to the varistor caused by aforcible fit. The varistor 18 has three electrode parts 19 fixed to thethree risers R2, R4, and R6 together with the winding 17 by soldering24. Only the winding 17 is connected to other risers R1, R3, and R5 bysoldering 25.

A small-diameter varistor 18 indicated by the phantom line in FIG. 1bcan also be attached to the position of a flange part 23 of thecommutator holder 20 from the armature core 11 side (lower face in thefigure). At this time, the flange part 23 of the commutator holder 20 isshrunk in diameter so as to fit to the annular inner face 22 of thevaristor 18.

FIGS. 4a and 4 b show embodiments of the varistor 18. FIG. 4a shows avaristor 18 a having three equal-sized electrode parts 19 a insulatedfrom each other on the outer peripheral side surface and an inner face22 a for a fit. FIG. 4b shows a varistor 18 b having three equal-sizedflat electrode parts 19 b insulated from each other along thecircumference on one face and an inner face 22 b for a fit. The numeral18 used above in the description denotes the varistor 18 a shown in FIG.4a.

That is, the varistor 18 a, the electrodes 19 a, and the inner face 22 ain FIG. 4a correspond to the varistor 18, the electrodes 19, and theinner face 22 respectively. The varistor 18 b shown in FIG. 4b can alsofunction as the varistor 18 by soldering the electrode parts 19 b to therisers R2, R4, and R6.

As described above, according to the small motor according to theinvention, a general ring varistor used with an armature of a 2-3(2-magnetic-pole—3-salient-pole) structure can be applied to a devicefor extinguishing spark arcs for suppressing overvoltage of an armatureof a 4-6 (4-magnetic-pole—6-salient-pole) structure without specialworking and moreover a special wiring pattern is not used, thuspart-to-part accuracy is not required and the structure and partsmanagement can be simplified sufficiently.

Because of coil winding according to a pattern drawn with a singlestroke of a brush, automation is facilitated and productivity can beimproved. Further, the varistor can be miniaturized, so that thearmature itself can be well fitted to miniaturization.

What is claimed is:
 1. A three-phase motor comprising: an armaturehaving six salient poles radially arranged and a three-phase coil woundaround said salient poles; six risers connected to said three-phasecoil; six commutators being joined to said risers in a one-to-onecorrespondence; a ring varistor being connected to some of said risersfor suppressing overvoltage; a brush coming in sliding contact with saidcommutators for supplying a current; and a permanent magnet having fourmagnetic poles, placed facing said salient poles; wherein said ringvaristor is provided with three electrode parts to which alternate threeof said six risers are connected, wherein a same phase portion of saidthree-phase coil has windings wound on a pair of said risers, one riserof said pair of risers being connected to one of said three electrodeparts, wherein said risers of said pair of risers are arrangedsymmetrically with respect to a rotation axis of said armature, andwherein at least one wire of said three-phase coil wound around saidsalient poles is the same wire wound on said pair of risers andconnecting together said pair of risers.
 2. The three-phase motor asclaimed in claim 1, wherein said six risers constitute three of saidpair of risers, and said risers in each pair are continuously connectedtogether.
 3. The three-phase motor as claimed in claim 1, wherein saidsix risers are connected together with said salient poles by a singlewire of said three-phase coil.
 4. The three-phase motor as claimed inclaim 1, wherein said six risers (1) respectively extend from said sixcommutators in a radial direction, and (2) are arranged to shift saidthree-phase coil extending from said salient poles in an axis direction,such that said three-phase coil is connected to said risers and connectssaid risers together.
 5. The three-phase motor as claimed in claim 4,wherein each of said risers has a protruded portion that extends beyondan outer peripheral portion of said ring varistor and said three-phasecoil is connected to said protruded portion.
 6. The three-phase motor asclaimed in claim 4, wherein each of said risers is circumferentiallypositioned between consecutive salient poles.
 7. The three-phase motoras claimed in claim 1, wherein all of the wires of said three-phase coilwound around said salient poles are also wound on said pair of risersand connect together said pair of risers.